Solid organic phosphite stabilizers are widely used as secondary antioxidants in polymer compositions. One commercially available antioxidant is tris(2,4-di-t-butylphenyl) phosphite, shown below, a solid antioxidant commonly known as Alkanox™ 240, Irgafos™ 168 and Doverphos™ S-480. U.S. Pat. No. 5,254,709, the entirety of which is incorporated herein by reference, describes the synthesis of tris(2,4-di-t-butylphenyl)phosphite by reacting 2,4-di-t-butyl phenol with phosphorus trichloride in the presence of catalyst. The isolated phosphite is described as a white crystalline solid melting between 180-185° C.

Tris(2,4-di-t-butylphenyl)phosphite has been demonstrated to effectively reduce peroxide induced oxidative degradation for many polymers including polyolefins, polycarbonates, ABS and polyesters. The trialkylaryl phosphite has low volatility that allows for its use at high temperatures commonly required for processing thermoplastic polymers. Owing to its solid form and concomitant processing limitations, however, tris(2,4-di-t-butylphenyl)phosphite is not well-suited for the stabilization of all polymers and has been demonstrated to plateout during processing of some plastics, in particular low melting point plastics, and forming deposits on processing machinery surfaces.
U.S. Pat. No. 5,254,709 also describes a solid tri(2,4-di-t-amylphenyl)phosphite and a solid mixture derived from 2,4-di-t-amyl phenol and 2,4-di-t-butyl-phenol.
Russian Patent No. RU 2 140 938 discloses a composition of synergists comprising three (2,4-di-t-butylphenyl)phosphites and combinations of other phosphites. The combination includes tri(2-t-butylphenyl)phosphite, tri-(4-t-butylphenyl)phosphite, di(4-t-butylphenyl)phosphite, di-(4-t-butylphenyl)(2,6-di-t-butylphenyl)phosphite and di(3-t-butylphenyl)(2,4,6-tri-t-butylphenyl)phosphite.
The need exists for novel solid phosphite compositions that are effective secondary antioxidants in polymers and in particular for effective solid phosphite compositions that have good processing characteristics.